Set up web server and php

tt-rss requires that the value of open_basedir is "none". You can set this /etc/php/php.ini (then sudo systemctl restart httpd).

tt-rss is installed into /usr/share/webapps/tt-rss/; you'll need to make this directory available from your web server. The simplest way is to do

# ln -s /usr/share/webapps/tt-rss /srv/http/tt-rss

Closing basedirs for non-tt-rss webapps

If you want the php open_basedir setting to only apply to the tt-rss location, you can add this to /etc/httpd/conf/httpd.conf:

<Location /tt-rss/>
php_admin_value open_basedir none
</Location>

However, this will make the update daemon (see below) fail. It might be able to fix it by making your own daemon that uses its own php.ini file, or simply a crontab entry like this (assuming you put the ini file into /etc/webapps/tt-rss: